1. Field of the Invention
The present invention relates generally to a combustor for a gas turbine engine having water injection for NOx abatement and, in particular, to a method of protecting selected components of such combustor from the effects of water erosion and hot corrosion.
2. Description of Related Art
It is well known that the combustor of a gas turbine engine is subjected to extreme temperatures during operation, perhaps as high as 3500.degree. F. Accordingly, several measures have been employed in the art to protect combustor components against thermal shock and high thermal stresses. These include the use of new and exotic metal alloys, various heat shield configurations, cooling schemes and certain types of thermal barrier coatings as demonstrated by U.S. Pat. No. 5,553,455 to Craig et al., U.S. Pat. No. 5,528,904 to Jones et al., U.S. Pat. No. 5,220,786 to Campbell, U.S. Pat. No. 4,655,044 to Dierberger et al., and U.S. Pat. No. 4,567,730 to Scott.
Another consideration involved with the design of gas turbine combustors is the ability to minimize emissions therefrom. In the case of marine and industrial applications, this has typically been accomplished through the injection of water into the combustor to reduce the temperature therein (e.g., through the nozzle circuit utilized for supplying fuel). It has been found, however, that such water injection has had the undesirable effect of causing metal distress and erosion to certain components of the combustor due to cavitation and impingement. The particular combustor components concerned may vary depending upon combustor design and exactly where impingement of the water takes place. It will be understood, however, that water is more punitive than other fluids passing through the combustor, such as liquid fuel and steam, because it has a higher coefficient of convective heat transfer and, all else being equal, causes higher thermal stress.
While some attempts have been made to solve both the thermal and erosion problems set forth above, such as in the Campbell patent, it will be noted that none of the heat shields employed have been subjected to water impingement. Thus, in light of the foregoing, it would be desirable for a new and improved method of protecting combustor components against water erosion and hot corrosion to be developed.